1. Field of the Invention
The invention relates to a resin connector for connecting a resin tube to a metal pipe or a resin-coated metal pipe having a relatively small diameter of about 40 mm or less and generally arranged in an automotive vehicle or various kinds of machines and apparatuses as a supply passage for supplying an oil and an air, and more particularly to a resin connector for connecting a pipe having a small diameter which can improve an extraction resisting force of a resin tube inserted into a connection cylinder wall and prevent the resin tube or a resin coated layer of the resin coated metal pipe from partly breaking by discharging a static electricity.
2. Description of the Prior Arts
Conventionally, various kinds of resin quick connectors for connecting a pipe having a small diameter have been suggested and put to practical use. In an embodiment thereof, for example, as shown in FIG. 12, the structure is made such that a small diameter chamber 23-1 expanded in continuous to a communication hole 24 of a connection cylinder wall 22 provided in a front end side of a resin connector main body 21 for inserting a resin tube C" and having saw-toothed projections on an outer peripheral portion and a large diameter chamber 23 are extended through the resin connector main body 21, a seal ring member 26 and a bush member 27 are installed in a portion of the small diameter chamber 23-1 of the resin connector main body 21, an independent socket body 28 having a plurality of hook walls 25 disposed in a front portion of a peripheral wall of a center hole in an axial core in an assembling direction and inclining inward is installed in an edge portion of an engaging hole 21-1 of a hooking wall 21-2 formed by a rear end peripheral portion of the engaging hole 21-1 pierced on a peripheral wall of the large diameter chamber 23 in a state of engaging a shoulder portion 25-1 of a base portion formed by the hook walls 25 and fitting a portion of an annular peripheral wall 25-2 disposed at a rear end side thereof, and a metal pipe P0 assembled in an inner portion or an annular expansion wall P0' of a resin coated metal pipe is connected by being pressed by the hook wall 25.
Further, as another embodiment, as shown in JP-A-9-280451 (Japanese Patent Application No. 8-121063) suggested by the applicant of the present application, the structure is made such that in an inner portion of an axial core, a small diameter chamber expanded in continuous to a communication hole of a connection cylinder wall provided in a front end side of a resin connector main body for inserting a resin tube and having saw-toothed projections on an outer peripheral portion and a large diameter chamber are extended through the resin connector main body, a seal ring member and a bush member are installed in a portion of the small diameter chamber of the resin connector main body, a socket body having an elastic wall projected forward and forming a hook wall by an inward inclined bending portion near a middle portion thereof so as to be urged inward and a protruding wall extended to an outer side of a peripheral wall of the connector main body from an outer end portion of the elastic wall is provided in a notched window portion disposed at an opposing portion formed by the peripheral wall of the large diameter chamber in such a manner as to be integral with the connector main body, and a connected metal pipe or an annular expansion wall of a resin coated metal pipe is connected to the elastic wall in accordance with pressing.
Still further, as the other embodiment, as shown in Japanese Utility Model Publication No. 7-24716, the structure is made such that in an inner portion of an axial core, a small diameter chamber expanded in continuous to a communication hole of a connection cylinder wall provided in a front end side of a resin connector main body for inserting a resin tube and having saw-toothed projections on an outer peripheral portion and a large diameter chamber are extended through the resin connector main body, a seal ring member and a bush member are installed in a portion of the small diameter chamber of the resin connector main body, an engaging hole is pierced on a peripheral wall of the large diameter chamber, and an independent socket body comprises an annular portion having an outer diameter substantially equal to an inner diameter of the small diameter chamber of the connector main body and an inner diameter substantially equal to an outer diameter of a metal pipe or a resin coated metal pipe and a plurality of elastic walls each having a projection extended from the annular portion and projected to an outer side of the middle portion and a notch notched at an inner side of the middle portion.
Then, the structure is made such as to insert the socket body within the small diameter chamber from the side of the annular portion via the large diameter chamber of the connector main body, press the notch provided on the elastic wall in such a manner as to be held in the metal pipe or the annular expanded wall of the resin coated metal pipe and fit the projection provided on the outer side of the elastic wall to the engaging hole provided on the peripheral wall of the expanded chamber in the connector main body, thereby connecting the metal pipe or the resin coated metal pipe to the connector main body.
However, in all of the conventional embodiments, when the extraction force is applied to the resin tube inserted into the connection cylinder wall of the resin connector main body, particularly under a heated circumstance, there is a case that the resin tube is extracted from the connector main body.
Then, in the case of the resin tube having a tendency of being easily extracted, it is unavoidable to fasten by a fastening band from the outer periphery of the inserted resin tube in order to prevent this, and accordingly a lot of labors are necessary for this operation, so that an improvement thereof has been desired.
It is not clear why the resin tube is easily extracted from the connection cylinder wall of the resin connector main body, particularly under a heated circumstance as mentioned above, however, it is estimated as follows, and this estimation will be described below with reference to FIG. 13.
That is, when an extracting force F is applied to the resin tube, at the same time of extending in an axial direction, the outer diameter and the inner diameter of the resin tube is shortened, so that a force f1 for pressing the connection cylinder wall in the side of the front end of the resin connector main body from the outer portion in a diametrical direction is applied thereto. On the contrary, a force f2 is applied to the inner peripheral surface of the connection cylinder wall from the inner portion in a diametrical direction in such a manner as to stand against the force f1, however, since the connection cylinder wall is thin, a sufficient opposing force f2 can not generated, so that the diameter of the connection cylinder wall is shortened due to the pressing force f1 and a friction force between the inner surface of the resin tube and the outer surface of the connection cylinder wall is lowered. Accordingly, it is felt that the resin tube becomes easily extracted.
Particularly, under the heated circumference, since a whole of the resin connector is softened, a rigidity is lowered and the opposing force f2 in the connection cylinder wall is generated at a significantly little amount, the tendency mentioned above becomes further significant.
Then, in order to improve the extraction resisting force of the resin tube, it has been considered that the connection cylinder wall of the connector main body is made thick, however, an inner diameter of the connection cylinder wall of the connector main body (that is, a diameter of the communication passage) d2 corresponds to a portion formed in a particular small inner diameter within all the pipe path, so that it is desired to make the inner diameter d2 as large as possible in order not to make a pressure loss of a fluid passing through the portion large.
Further, since it is hard to insert and assemble the resin tube when setting an outer diameter D2 of the connection cylinder wall large, it is desired to make it as small as possible.
Due to the limiting conditions of the inner diameter and the outer diameter of the connection cylinder wall as mentioned above, it has been impossible to make the connection cylinder wall thick.
Further, in the case of inserting and connecting the resin tube to the connector for resin pipe having a small diameter and using it to a fuel pipe system, the following problems existed.
That is, when a fuel such as a gasoline passes within the fuel pipe system, a static electricity is generated due to a fluid friction with respect to the inner wall surface of the pipe or a fluid friction with respect to a filter in the flow passage. On the contrary, a connecting connector used for connecting an engine side pipe and a fuel tank side pipe to the resin tube and connecting each of the resin tubes to the fuel pipe has an insulating characteristic because it is formed by a resin material, the resin tube used for the fuel pipe system has an insulating characteristic because it is constituted by a rubber tube or a nylon tube, and further, in the case of employing the resin coated metal pipe, the resin coated layer applied to the outer peripheral surface has an insulating characteristic. Accordingly, a static electricity generated due to the fluid friction with respect to the inner wall surface of the pipe or the fluid friction with respect to the filter in the flow passage as mentioned above is not discharged in the connecting connector, the resin tube and the resin coated layer of the resin coated metal pipe but is still charged.
In this case, the rubber tube used as the resin tube generally has a thickness of about 3 mm, and the nylon tube has a thickness of about 1 mm.
Then, the static electricity generated due to the fluid friction with respect to the inner wall surface of the pipe as mentioned above is gradually charged without being discharged because an insulating material is employed for the part constituting the fuel pipe system, and generates a spark at a nearest portion to a vehicle body on an outer peripheral surface of a thin portion of the resin tube or the resin coated layer of the resin coated metal pipe when reaching 1000 V or more, and the resin tube or the resin coated layer is partly broken by this spark. This broken portion forms a pin hole, and a damage of the resin tube or the metal pipe is partly begun from the pin hole portion.